NEW DELHI: A 24-year-old ruling was invoked in the Rajya Sabha on Friday to deny the Opposition a chance from seeking clarifications from Prime Minister Manmohan Singh on his statement on the cash-for-vote scandal.

As angry Opposition members demanded to know why rules had changed overnight, Rajya Sabha Chairman Hamid Ansari cited a 1987 ruling when the then prime minister had made a statement relating to the purchase of Bofors guns from Sweden.

The Chair had ruled then "if the Prime Minister makes a suo motu statement you are entitled to ask him for clarification. Now the Prime Minister's statement is just in response to your question. Tomorrow there is going to be a full-dress debate on defence. You can raise all these points there and the minister concerned will reply."

Ansari said Singh's statement too was not made suo motu but on the Opposition's demand. Taken aback, the Opposition members who were all set to seek the customary clarifications were up on their feet. "The practice till last week was that clarification is sought whenever any minister speaks. I don't know why that convention is broken today," asked Opposition leader of the House Arun Jaitley. CPM's Sitaram Yechury wanted to know why the government remembered the rule after so many years.

Parliamentary Affairs Minister Pawan Kumar Bansal said that if the statement was suo motu, the clarification could be demanded. "The subject was chosen by them (opposition), the House has not been running for some time. We can't go by what they wish. What else would satisfy them," Bansal said.

Opposition members trooped into the well of House, forcing Ansari to adjourn the House for the day.

Later, addressing a press conference, Jaitley said "Opposition was being gagged by the chair not allowing us to seek clarification on PM's statement on the WikiLeaks." He also pointed out that the ruling Ansari referred to was in relation to the Bofors case.

Jaitley said then a debate took place after two days while no discussion was scheduled now in the case of the cash-for-vote issue. His counterpart in the Lok Sabha Sushma Swaraj said the NDA had already given a notice for a debate on the issue under Rule 193 in Lok Sabha, where rules did not permit clarifications.

In a lighter vein, she referred to reports of disconnect between the two leaders of Opposition in strategy adopted in both Houses saying "the presiding officers made things easier."